1. Field of the Invention
The present invention relates generally to a probe card, and more particularly to a probe card capable of distributing a signal to several terminals.
2. Description of the Related Art
In the process of fabricating integrated circuit (IC), probe card is used to test integrated circuits on a wafer prior to packaging process. Typically, probe card electrically connects a tester and devices under test (DUTs), each of which includes an integrated circuit. The probe card has needles firmly contacted to the integrated circuits to test the function of the integrated circuits of DUTs. The faulted DUTs are marked to find the yield rate of the integrated circuits, and then performing packaging process. Probe card is the most important device for testing process that it is very important in the processes of fabricating integrated circuit.
However, it usually causes a signal integrity problem in the circuit of the conventional probe card, which will cause errors in the testing process. Besides, the number of tested DUTs at a time is restricted by the number of the signal channels of the tester, which will cause a limitation of the number of DUTs for test and the speed of test, and therefore slows down the efficiency of fabrication. So, how to provide an improved probe card circuit in association with the conventional tester in order to increase the signal channels for a high testing efficiency and improve the integrity in signal transmission for a high testing quality is an important problem to be solved.
U.S. Pat. No. 6,965,248 provides an improved circuit of a probe card to increase signal channels through a set of resistors and a compensative circuit. However, it will cause a loading effect between the channels while the number of the channels is increased, which needs a complex compensative circuit to fix. On the other words, the probe card referred here still has problems in real application. U.S. Pat. No. 7,012,442 discloses a system for increasing signal channels which employs a set of resistors to form a distribution network, and it will have a poor signal transmission quality and high signal power loss and noise because of the impedance matching in a high operation frequency.
To overcome the drawbacks of the prior art, the present inventors invented a probe card through a series of tests and studies. It employs the functions of analog-to-digital conversion and power distribution of analog signal in association with serialization of digital signal to increase the number of the signal channels and raise the integrity and separation of signal transmission and reduce the signal power loss and noise.